What is the difference between living longer and living longer in good health (healthspan)?

Lifespan is the total number of years you live; healthspan is the period within that during which you are healthy and functional. The two diverge in measurable ways. Research into biological ageing shows that a person with a calendar age of 50 can already be biologically closer to 65, with a correspondingly higher risk of early death, cancer, reduced physical functioning, and Alzheimer's disease. Conversely, someone can be biologically younger than their passport suggests. Living longer without those additional healthy years is explicitly not the goal of modern ageing research.

Why does healthspan run out sooner than lifespan? Two processes play a central role. First, cells that have aged and can no longer divide accumulate in tissues. They do not die off, but they do continuously secrete inflammatory substances that damage surrounding tissue and drive disease. Second, the internal clean-up system of cells, which breaks down and recycles damaged material, weakens over time. When that system functions less effectively, damaged proteins and cell components build up. Both processes erode quality of life long before they become fatal.

What can you do about it? Caloric restriction with adequate nutrition is the best-supported approach: in rodents and primates it extends both healthy and total lifespan, partly by activating the clean-up processes mentioned above. Intermittent fasting has comparable mechanistic effects and appears to be safe, although the evidence in humans for lifespan extension is not yet conclusive. The gut microbiome also plays a role: in mice with accelerated ageing, a transplant of healthy gut bacteria improved health and lifespan, but this has not yet been translated to ordinary humans.

NMN supplements (a precursor to NAD+, a substance that cells need for energy and repair) are popular, but the evidence is preliminary. In a small RCT of 80 middle-aged adults over 60 days, NAD levels rose at all doses, walking distance improved, and participants reported better health. The study was short, the group was small, and one author was employed by the manufacturer. The latter does not undermine the findings as such, but calls for caution until larger independent studies confirm them. Senolytics, agents that clear out worn-out cells, appear promising in animal models, but clinical evidence in humans is still very limited.